Suction jet pump and method for producing a nozzle for a suction jet pump

ABSTRACT

A suction jet pump provided for the conveyance of fuel in a fuel tank has a separate nozzle insert with a nozzle duct. The nozzle insert can be produced both from plastic by the injection-molding method or from metal. By virtue of the smaller component size in the case of plastic or due to the choice of metal as material for the nozzle insert, the nozzle duct can be provided with a particularly small diameter. The suction jet pump has a particularly low propellant consumption.

CLAIM FOR PRIORITY

[0001] This application claims priority to Application No. DE 10119553.2 which was filed in the German language on Apr. 21, 2002.

TECHNICAL FIELD OF THE INVENTION

[0002] The invention relates to a suction jet pump, and in particular, a suction jet pump provided for the conveyance of fuel in a fuel tank, with a nozzle which is arranged upstream of a mixing tube and is capable of being connected to a propellant line and which has a nozzle duct. The invention relates, furthermore, to a method for producing a nozzle for a suction jet pump.

BACKGROUND OF THE INVENTION

[0003] Suction jet pumps are often used in fuel tanks of present-day motor vehicles in order to convey fuel out of one chamber of the fuel tank into another chamber or in order to fill a baffle. The nozzle of these suction jet pump is typically manufactured from a plastic POM in one piece together with a casing. An injection mold is used for producing the nozzle. The nozzle duct is made by a core of the injection mold during the production of the nozzle by the injection-molding method.

[0004] The suction jet pump has the disadvantage that the nozzle duct possesses a very large diameter of usually 0.5 mm. The suction jet pump consequently has a very high consumption of propellant. This leads to a high energy consumption of a feed pump supplying the suction jet pump with propellant. A reduction in the diameter of the nozzle duct is usually not possible because of the very large casing dimensions in relation to the nozzle duct. This is because, for stability reasons, the diameter of the core should not fall short of a diameter of approximately 0.5 mm. With this diameter of the nozzle duct, the suction jet pump has a propellant consumption of 25 liters per hour. It is not possible for the nozzle duct to be made by subsequent drilling of the nozzle manufactured without a core by the injection-molding method, since the plastic may fray, resulting in a high frictional loss during the subsequent through-flow of propellant. A further problem which prevents the nozzle duct from being reduced arises in suction jet pumps, the nozzle casing of which is closed by means of an end cap on the side facing away from the nozzle duct. The two parts are welded to one another in order to achieve a leak-tight closure. Impurities occur during the welding process and may settle in the nozzle duct. The problem on which the invention is based is to design a suction jet pump of the type initially mentioned, in such a way that it has a particularly low consumption of propellant. Furthermore, a method is to be provided for the manufacture of a nozzle for a suction jet pump having a particularly low consumption of propellant.

SUMMARY OF THE INVENTION

[0005] In one embodiment according to the invention, the nozzle has a nozzle insert as a separate component. The size of the component receiving the nozzle duct is reduced, so that, to produce the nozzle insert as an injection molded part, smaller dies can be employed which make it possible to use cores with a substantially smaller diameter. Thus, without higher outlay, nozzle ducts of, for example, 0.3 mm can be produced with a high degree of process control by the injection-molding method. These nozzle inserts can therefore be manufactured particularly cost-effectively from POM.

[0006] In another embodiment, the nozzle insert is manufactured from metal. As a result, the nozzle duct can be produced from metal, with a particularly small diameter in the insert, by various manufacturing methods. For example, by virtue of the invention, nozzle ducts with a diameter of 0.3 mm can be produced even in metal at a low outlay.

[0007] The suction jet pump according to the invention, with a diameter of the nozzle duct of 0.3 mm, has a propellant consumption of approximately 10 liters per hour. The suction jet pump according to the invention consequently has a particularly low consumption of propellant. The suction jet pump according to the invention has particularly low energy consumption. A further advantage of this design is that a cavitation in the region of the nozzle duct can be largely prevented by a suitable selection of a plastic or of a metal for the nozzle insert. The suction jet pump according to the invention therefore has a uniformly high conveying capacity.

[0008] According to another advantageous embodiment of the invention, the nozzle can be manufactured particularly cost-effectively when the metal of the nozzle insert is brass.

[0009] The manufacture of the suction jet pump according to the invention for various fields of use in different intended pump capacities becomes particularly simple when the nozzle has a nozzle casing with a connection for the propellant line and the nozzle casing is designed for holding the nozzle insert. The nozzle insert can thereby be assembled together with standard nozzle casings for intended fields of use of the suction jet pump. In addition, owing to the insertable nozzle insert, the nozzle casing can now be made in one part, since the nozzle insert is now an element which closes the nozzle casing. There is therefore no need for an end cap to be welded onto the nozzle casing.

[0010] According to another advantageous embodiment of the invention, the fastening of the nozzle insert to the nozzle casing becomes particularly simple when the nozzle insert has a bowl-shaped design and engages over an edge of the nozzle casing.

[0011] When manufacturing a nozzle for a suction jet pump having a particularly low consumption of propellant, it is preferable that the nozzle insert is produced from plastic, preferably POM, by the injection-molding method, the nozzle duct being made during injection molding.

[0012] In another embodiment, after the manufacture of the nozzle insert from metal or plastic, the nozzle duct is worked into the latter. According to another advantageous embodiment, nozzle ducts with a particularly small diameter can be made in the nozzle insert in a simple way when the nozzle duct is worked in by means of a laser beam.

[0013] However, according to an advantageous embodiment of the invention, the manufacture of the nozzle duct in a nozzle insert made of metal requires particularly low outlay in terms of a manufacturing plant when the nozzle duct is worked into the nozzle insert by means of a drilling tool. The erosion method may be envisaged as a further advantageous embodiment.

[0014] According to still another advantageous embodiment of the invention, the manufacture of the nozzle becomes particularly cost-effective when the nozzle insert and the nozzle casing are pressed together with one another or are snapped together by means of latching elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention permits numerous embodiments. These are illustrated in the drawings and are described below. In the drawings:

[0016]FIG. 1 shows a diagrammatic illustration of a suction jet pump according to the invention.

[0017]FIG. 2 shows a section illustration of the nozzle of the section jet pump according to the invention from FIG. 1 before assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018]FIG. 1 shows diagrammatically a suction jet pump with a nozzle 1 and with a mixing tube 2. The nozzle 1 has a connection 3 for a propellant line, not illustrated. The mixing tube 2 has a mixing region 4, in which propellant conveyed through the nozzle 1 and liquid sucked in from the region between the nozzle 1 and the mixing tube 2 are mixed. The liquid subsequently passes, together with the propellant, into a diffuser 5. The mixing tube 2 is illustrated as being cut away. Furthermore, flows of the propellant and of sucked-in liquid are marked by arrows. Such a suction jet pump is suitable, in particular, for the conveyance of fuel within a fuel tank, not illustrated, of a motor vehicle.

[0019]FIG. 2 shows a sectional illustration of the nozzle 1 before its assembly. The nozzle 1 has a nozzle casing 6 and a nozzle insert 7. The nozzle casing 6 is, in this example, manufactured from plastic by the injection-molding method, while the nozzle insert 7 consists of POM. A nozzle duct 8 is arranged in the nozzle insert 7. The nozzle duct 8 was made by means of a core in the injection-molding die. The nozzle casing 6 has a projecting edge 9, over which the nozzle insert 7 engages in the assembled state. The nozzle casing 6 and the nozzle insert 7 are connected to one another by being pressed together. The nozzle insert 7 has a projection 10. In the assembled state of the nozzle 1, the projection 10 penetrates into a groove 11 arranged in the edge 9 of the nozzle casing 6. The nozzle insert 7 and the nozzle casing 6 can thereby be reliably connected to one another. Arranged on the nozzle casing 6 is a latching hook 12, by means of which the suction jet pump can be snapped together with adjacent components.

[0020] The mixing tube 2, illustrated in FIG. 1, and the nozzle casing 6 can be manufactured jointly from the plastic POM and, for example, can be adhesively bonded or welded to one another. 

What is claimed is:
 1. A suction jet pump for the conveyance of fuel in a fuel tank, comprising: a nozzle arranged upstream of a mixing tube and configured for connection to a propellant line; and a nozzle duct, wherein the nozzle has a nozzle insert in the region of the nozzle duct.
 2. The suction jet pump as claimed in claim 1, wherein the nozzle insert consists of plastic.
 3. The suction jet pump as claimed in claim 1, wherein the nozzle insert consists of a metal.
 4. The suction jet pump as claimed in claim 1, wherein the nozzle has a nozzle casing with a connection for the propellant line, and the nozzle casing is configured for holding the nozzle insert.
 5. The suction jet pump as claimed in claim 1, wherein the nozzle insert is of bowl-shaped design and engages over an edge of the nozzle casing.
 6. A method for producing a nozzle for a suction jet pump having a nozzle arranged upstream of a mixing tube and configured for connection to a propellant line and a nozzle duct, wherein the nozzle has a nozzle insert in the region of the nozzle duct, comprising: manufacturing the nozzle insert as a separate component from plastic by the injection-molding method, the nozzle duct being made during injection molding.
 7. A method for producing a nozzle for a suction jet pump having a nozzle arranged upstream of a mixing tube and configured for connection to a propellant line and a nozzle duct, wherein the nozzle has a nozzle insert in the region of the nozzle duct, comprising: working the nozzle duct into plastic, after the manufacture of the nozzle insert from metal or plastic.
 8. The method as claimed in claim 7, wherein the nozzle duct is worked into the nozzle insert by means of a drilling tool.
 9. The method as claimed in claim 7, wherein the nozzle duct is worked into the nozzle insert by means of a laser beam or by the erosion method.
 10. The method as claimed in claim 7, wherein the nozzle insert and the nozzle casing are pressed or snapped together with one another.
 11. The method as claimed in claim 6, wherein the nozzle insert and the nozzle casing are pressed or snapped together with one another. 